The long term objective of this research project is to gain an understanding of how gene expression is controlled at the molecular level. Frog virus 3 (FV 3) replication in eukaryotic cells is used as a model system in meeting this objective. A physical, genetic, and transcriptional map of the FV 3 genome will be obtained utilizing the combined techniques of restriction endonuclease digestion and electron microscopy of DNA molecules. Marker rescue of ts mutants will be used to construct a genetic map. Transcriptional mapping will utilize molecular hybridization of individual FV 3 mRNA species to restrictive endonuclease fragments. Structural proteins of FV 3 will be isolated and characterized. Efforts will be made to identify biological functions of purified virion-associated proteins such as enzyme activities, switch-off and nongenetic reactivation. We will also investigate the mechanism of translational control of host cell protein synthesis by FV 3 switch-off protein(s), and the mechanisms of translational control of viral protein synthesis by viral proteins. We will attempt to regulate the translation of virus-specific mRNAs in vitro; ts mutants with altered translational control will be utilized extensively in this portion of the research. Mechanisms of transcriptional control in FV 3-infected cells will be analyzed. Methods to be used include standard virological, biochemical, and molecular biological ones and include hybridization, gel electrophoresis, peptide mapping and cell-free systems of protein synthesis.